The present disclosure relates to a display apparatus, and more particularly to a display apparatus using a head mounted display (HMD).
JP-A-2006-162767, for example, discloses a virtual image display apparatus (image display apparatus) that allows a viewer to view a two-dimensional image formed by an image formation device in the form of an enlarged virtual image through a virtual image optical system.
As shown in FIG. 7, which is a conceptual diagram, an image display apparatus 100 includes an image formation device 111 in which a plurality of pixels are arranged in a two-dimensional matrix, a collimator optical system 112 that collimates light having exited from the pixels in the image formation apparatus 111, and an optical device (light guide means) 120 on which the collimated light from the collimator optical system 112 is incident, through which the light is guided, and out of which the light exits. The optical device 120 includes a light guide plate 121 through which light incident thereon propagates while undergoing total reflection and out of which the light exits, first deflection means 130 (formed, for example, of a light reflection monolayer film) that reflects the light incident on the light guide plate 121 in such a way that the light incident on the light guide plate 121 undergoes total reflection therein, and second deflection means 140 (formed, for example, of a light reflection multilayer film having a multilayer stacked structure) that outputs the light having propagated through the light guide plate 121 while undergone total reflection out of the light guide plate 121. An HMD or any other display apparatus formed of the thus configured image display apparatus 100 can be lightweight and compact.
JP-A-2007-94175, for example, alternatively discloses a virtual image display apparatus (image display apparatus) using a hologram diffraction grating to allow a viewer to view a two-dimensional image formed by an image formation device in the form of an enlarged virtual image through a virtual image optical system.
As shown in FIG. 11A, which is a conceptual diagram, an image display apparatus 300 basically includes an image formation device 111 that displays an image, a collimator optical system 112, and an optical device (light guide means) 320 on which the image displayed by the image formation apparatus 111 is incident and through which the image is guided to a pupil 21 of a viewer. The optical device 320 includes a light guide plate 321 and first and second diffraction grating members 330, 340, each of which is formed of a reflective volume hologram diffraction grating provided on the light guide plate 321. Light having exited from each pixel in the image formation device 111 is incident on the collimator optical system 112, which produces collimated light, which is then incident on the light guide plate 321. The collimated light is incident on a first surface 322 of the light guide plate 321 and exits therethrough. On the other hand, the first diffraction grating member 330 and the second diffraction grating member 340 are attached to a second surface 323 of the light guide plate 321, which is parallel to the first surface 322 of the light guide plate 321.
When an image of a caption or any other information is displayed in the image display apparatus 100 or 300, a viewer can view the displayed image superimposed on an outside-world image (a player in a play, moving pictures in a movie, for example).